TRD is developing a supercharger for the IS-F. Mules are testing it right now, the target is 625 bhp
I would say more like 550hp conservatively. Roots type blowers are limited unlike turbos. they are parasitic, takes power to make power. so about 125 hp added is more realistic.I talked with my Lexus dealer last month about warantee issues. If TRD releases the supercharger for the IS-F and it is installed by the Lexus dealer, the warantee will not be voided. Since all of our F's are so new it would be nice to be able to retain the warantee and also have the supercharger. Since 417 hp is so much fun, just immagine how much fun 625 would be.
ASp Made the pulley for me back in 2002, The want 150 for it but i can get it much cheaper than that from them. This pulley replaces the stock crank pulley and you will need a smaller serpentine belt . You can free up about 15 hp on a tundra so I would think about 20 easy on the Is-f. plus its alluminum,
less rotating weight.